Chuck Prince, the chief executive of Citigroup, called 2007 "the year of no excuses". In a disastrous year that has seen the share price dive 31%, each piece of bad news brought the excuses flowing thick and fast. Yesterday they ran out.

For Wall Street, Mr Prince's departure ushers in a chance for change and a possible break-up of the world's largest bank. But for the 57-year-old lawyer it ends a career at the bank that has spanned almost three decades.

After four years at the helm, his exit also draws a line under a tenure that never quite managed to gain the full confidence of his peers and colleagues.

When he took on the chief executive role from Citigroup's flamboyant founder Sandy Weill, the California lawyer had immense shoes to fill. Whereas his Brooklyn-born predecessor, a former stockbroker, commanded great respect on Wall Street, Prince has always been viewed as an outsider.

Born in 1950, Charles O Prince III gained a law degree and a master's in international relations from the University of Southern California and a master's degree in law from Georgetown University in Washington DC before starting his working life as an attorney at US Steel Corporation.

In 1979 he joined Commercial Credit Company, which later became part of the Citigroup conglomerate built through a raft of deals by Mr Weill in his bid to create a one-stop financial "supermarket".

For much of that process Mr Prince was by the empire-builder's side as his chief lawyer. He became his close friend as well - the two have taken joint holidays and are even said to have dieted together.

It was in 1998 that Mr Weill pushed through the deal that created the banking behemoth now known as Citigroup by merging Travelers with Citicorp.

When Mr Weill announced his decision to stand down as chief executive in 2003, there were several contenders for the job but it was his close ally Mr Prince who won.

Mr Prince told the world, in front of his mentor, "the Sandy Weill show is done" but Citigroup's founder, then 70, kept his chairman role. Indeed, Mr Prince's appointment was widely interpreted as a sign that Mr Weill was not ready to relinquish control.

Whereas Mr Weill achieved a kind of rock star status on Wall Street, Mr Prince was never able to shake off the lawyer label. Still, many observers had sympathy with him, noting his reign followed a prolonged era of under-investment, during which Mr Weill had snapped up businesses but rarely integrated them properly.

There was a difficult road ahead, marked by a private banking scandal in Japan, dodgy European bond deals and huge payouts to investors burned by the collapses of Enron and WorldCom.

Mr Prince, who took over the chairman role from Mr Weill in 2006, tried to stamp a more moral tone on the group's business practices. He also went on a drive to break down bureaucracy and drive up efficiency, but that push has had little effect on Citigroup's share price. Disappointing results were accompanied by the departures of several senior figures, losing Mr Prince vital allies inside the bank.

He claimed he wanted to keep Citigroup out of the headlines but the credit crunch only drove up the column inches. And for the boss whose credibility was never rock solid on Wall Street, it was only a matter of time before the attention would turn to his own future.